@AreYouShiveringI think because those are new accounts. By default, you play as Lifeline. Its easier to make a script to click "ready" in the lobby and jump into a match, then to make the script switch legends, then jump into a match.
If a real player took Lifeline, or there was two bots on the same team, you'll start seeing Bangalore, as the auto legend picker chooses the next legend you have the highest kills on. Since its a bot account that's only AFKing to level up to hit level 50, Bangalore is the first one on the legend select screen, so she gets selected.
I haven't seen anyone complain about a 3rd legend afking like that, but if does happen, it would most likely be Fuse since he's the second legend on the legend select screen.
I know the legend select screen picks the legend with the next highest amount of kills because if I choose Revenant, and he gets taken, it auto selects Wraith. If the randoms took Wraith and Revenant, it auto selects Valkyrie. If the randoms took Wraith and Valkyrie, it auto selects Lifeline.
Current Kills:
Wraith - 3711
Valkyrie - 3426
Lifeline - 1763
My 4th highest is Pathfinder with 842, everyone else I rarely play as, so they're between 1 and 500 kills.
These bots all punch the air to reset the AFK timer. There should be a system like Overwatch where you HAVE to move.
